The prostate gland is a site of significant pathology affected by conditions such as benign growth (BPH), neoplasia (prostatic cancer) and infection (prostatitis). Prostate cancer represents the second leading cause of death from cancer in man. However, prostate cancer is the leading site for cancer development in men. The difference between these two facts relates to prostatic cancer occurring with increasing frequency as men age, especially in the ages beyond 60, at a time when death from other factors often intervenes. Also, the spectrum of biologic aggressiveness of prostatic cancer is great, so that in some men following detection the tumor remains a latent histologic tumor and does not become clinically significant, whereas in other patients it progresses rapidly, metastasizes and kills the man in a relatively short 2 through 5 year period.
Prostate specific antigen (PSA) is a tissue specific glycoprotein which can only be found in the prostate gland and its secretions. Because of the tissue specificity of PSA, it is well known to be a unique indicator for the prostate function as described by Hara, M., et al., Two prostate specific antigens gamma-semino-protein and beta-microsemino-protein, J. Lab. Clin. Med. 1989; 113: 541-48. PSA is therefore a particularly useful indicator in controlling patients after radical prostatectomy, and determining whether they suffer any further appearance of their prostate cancer because the operative intervention should have removed the entire prostate tissue and therewith also the possible source for releasing prostate specific antigen. In patients with a prostate cancer, in whom, through histological examination the cancer has been proven to be limited to the prostate organ, the value of PSA after radical prostatectomy falls under the detection level of the presently available immunoassays in 80-92% of the cases. A further increase in the PSA value is the earliest available indicator for a further appearance of the cancer after a complete prostatectomy.
Although the detection of PSA has certainly proved to be an indicator of the presence of prostate cancer, there is an unacceptable number of patients who have normal or near normal PSA serum levels but have prostate cancer. In addition, there are a large number of patients with abnormally high PSA serum levels that have a benign tumor.
Recently, it has been reported that measuring the ratio of free PSA to bound PSA in the serum is a more accurate method of diagnosing prostate cancer. However, this method, while reportedly more accurate in diagnosing prostate cancer than free PSA only, still misses a high number of patients with prostate cancer.
What is needed is a method that can be easily administered and accurately diagnose or provide prognosis for the presence of prostate cancer, preferably in its early stages.